Ergonomics is about safe and efficient use of the human body, with minimum strain and in a way which is comfortable when working, cooking, driving, creating, or wheeling. Continuous muscular effort, even in the form of small exertions continuously held can be as stressful as brief, heavy effort. Leaning on armrests can put continuous load on your shoulders. This is an example of “static” exertion, which is often due to a poor relationship to the seat and back of a chair. Poor posture is an overexertion, wherein slumping or leaning forward causes the body's trunk, neck and shoulder muscles have to do a lot of continuous work. People often spend a lot of time leaning on armrests or a table due to lack of support with good posture in their chairs, resulting from improper seat angle and back angle. The optimal ergonomic posture is more upright, allowing the spine to support the body.
It is known in the art that to protect the health and well being of today's worker, it is necessary to organize the worker's environment around sound ergonomic principles. For many types of work, suitable seating that permits a worker to engage in assigned tasks with minimum physical stresses is considered essential. Such ergonomic principles apply equally to workers while confined temporarily or permanently by disability to a wheelchair. These principles are described in some detail in U.S. Pat. Nos. 6,644,748, 6,702,372, and 6,726,276 all of which are hereby incorporated by reference. The chair disclosed by Thoelkes et al. (U.S. Pat. No. 7,367,623) adheres to many of these ergonomic principles, but among other things, does not provide for mobility.
Prior to the conception and development of the present invention, as is generally well known in the related art, most wheelchair designs provide seating compatible with standard table height (about 30 inches), which limits the height to which the occupant can reach. Such designs do not generally support the optimal more upright ergonomic posture that allows the spine to support the body. In addition, most wheelchair designs are too large for rotation in a narrow passageway, which requires their operation forwards or backwards. During backward movement the occupant is more limited in terms of rearward visibility and operations that can be performed. One approach to addressing these problems is the reversible chair disclosed by Moran, et al. (U.S. Pat. No. 7,547,031). In Moran, et at the seat can be elevated to clear the top of the drive wheels and rotated for operation of the chair in a reverse direction, however, the seat arrangement does not provide for optimal ergonomic posture. The occupant may be able to use the elevation feature to gain greater reach in height, however doing so may result in instability, particularly if the occupant attempts to extend a more horizontal reach. It is stated in Moran that having the drive wheels forward of the guide wheels is preferable for use on rough ground or uneven surfaces. However, contrary to this, the rotating seat of Moran can configure the drive wheels aft of the guide wheels in some situations. A mobility chair capable of a turning maneuver in a narrow passageway, and proving for optimal ergonomic posture and greater occupant reach while maintaining stability, is needed.